Ligation of vessels or other anatomical structures is a common step in a large number of surgical procedures. Traditionally, a ligation procedure comprises the placement of a suture about the target vessel or anatomical structure (e.g. artery, vein, duct, Fallopian tube, etc.) and tying off the suture to close the vessel, conduit or structure. The effective use of sutures to accomplish this procedure relies on the skillful execution of complex knots using a needle and thread. The space and time needed for this process limits the efficacy of suture-based ligation techniques, particularly in endoscopic or laparoscopic surgeries. The restrictions to freedom of movement incumbent in the use of minimally invasive surgical techniques present a significant challenge to the surgeon when ligating target vessels or structures with sutures.
The use of ligation clips in open and endoscopic surgical procedures addresses many of the shortcomings of suture-based ligation. Ligation clips are commonly applied with a tool specifically designed to hold and securely apply the clip to a target vessel or the like. Various types of ligation clips are commercially available, and can be broadly grouped into symmetric or asymmetric designs fabricated from metallic or polymeric materials. The metallic clips are typically symmetric in shape (e.g. U or V shaped) and fabricated from materials including, but not limited to, stainless steel, titanium, tantalum, and alloys thereof. The metallic clips are placed around the target vessel and permanently (i.e. plastically) deformed to close and restrict flow through the target vessel. While functional, the design and material components of metallic clips limit their use under the state of the art. For example, metallic clips cannot be used in patients that may undergo magnetic resonance imaging (MRI) or computed tomography (CT) as the clips can interfere with the signals used in those imaging modalities. Furthermore, since the metallic clips are closed via permanent deformation of the clip itself, an inherent limit is placed on the size vessel a given size of metallic clip can close (i.e. the high magnitude of deformation required to close a metallic clip about a larger diameter vessel may weaken the metal and induce a break or other failure in the structure of the clip) resulting in potentially catastrophic clinical consequences.
Polymeric ligation clips provide an alternative to metallic clips with several important differences. One such difference is the compatibility of polymeric clips with state of the art imaging modalities (e.g. MRI, CT, etc.). For example, polymeric ligation clips are non-magnetic and can be used in patients that will likely undergo MRI in the future. A second difference is in the means of maintaining the clips in closed state about the target vessel. Polymeric ligation clips are not typically plastically deformed about the target vessel; instead, the clips include design features that employ locking or latching mechanisms to hold the clip in a closed state. This offers an advantage over metallic, plastically deformable clips, in that a larger vessel for a given clip size may be closed with a plastic locking clip (as opposed to a plastically deformable clip of similar size), provided the locking mechanism is strong or robust enough to maintain the clip in the closed or securely locked position. Polymeric clips may further be divided into those that are intended for permanent residence in the patient following the surgical procedure and those that are designed to degrade after a specified amount of time post-implantation.
A ligation clip that can pinch or retain the target vessel or tissue or a part thereof, for example into the jaws of the clip prior to the clip reaching the fully closed position, provides a clip that is easier and more reliable to use. A clip that can secure the vessel or tissue in a position close to the hinge or junction of the clip as the jaws close provides for increased utilization of the available clip space. Also, a clip that can draw or pull the pinched vessel or tissue towards the hinge or junction section when the clip is closing and/or retain it there when the clip is fully closed and locked provides a more reliable and useful clip. Furthermore, a ligation clip comprising a robust means of piercing through or penetrating tissue that is attached to the target vessel and may interfere with the closing and/or locking of the ligation clip also improves the use and reliability of ligation clips.